The Met Office & The Pause
By Paul Homewood
There has been much discussion about “The Pause” in recent days, and not just here.
There was one comment, however, over at WUWT which caught my eye. To paraphrase, it stated that the only dataset which showed a pause in temperatures was RSS, and questioned whether we should be placing over reliance on this single set.
So, I thought we should take a closer look, and see how true this is.
First though, a few points to note:
1) I am using the term “pause”, in the colloquial sense, to denote a period where there has been no warming trend. This would therefore incorporate periods of cooling. Warmists often try to use misdirection by talking about “slowdown in warming”, so we need to address this.
2) Nothing in nature ever stays exactly the same, and the temperature record inevitably has ups and downs, which at various times will produce small warming and cooling trends. This is why it is important to differentiate between statistically significant and insignificant trends.
3) We are familiar with claims that, for instance, RSS shows no warming trend since December 1996. While there are different starting points since then which may show some warming, the logic is that this is as far back you can go and find no warming.
4) The purpose of this post is not to analyse why the pause has occurred, nor to forecast how long it will last and what will happen afterwards. I have already made my views clear on this, as far as ocean cycles go (see the AMO tag).
As we are up to over 60 attempts to explain away the pause, I think we can safely leave this topic till another day!
So, is it true that only RSS show the pause? Certainly not, as we know that the new UAH Version 6.0 closely follows the RSS data. (Unfortunately, Woodfortrees have not yet updated recent UAH data).
But what about the surface datasets?
Here we need to revisit the report which the UK Met Office published in July 2013.
The Executive Summary alone mentions the word “pause” eleven times, but the key paragraph is this:
It is often claimed that the “pause” only arises from cherry picking the El Nino year of 1998 as the starting point.The Met Office makes it clear that the El Nino effect was cancelled out by the La NIna which followed, and that the pause was a genuine phenomenon after 2000.
So, what was it exactly that they were seeing at the time they wrote the report? We can see the HADCRUT trends from Woodfortrees.
The blue trend line (actually up to the end of 2013) is totally flat (actually – 0.001C/decade). This is what the Met Office would have seen at the time.
I have also shown the latest trend (green line), and it can be seen the effect which El Nino conditions over the last year have had, as the trend is now slightly up at 0.02C/decade, which is still a tiny and statistically insignificant number.
It is true that GISS and NCDC show slightly higher trends than HADCRUT. It should be pointed out here that these cannot be regarded as two independent datasets, since both rely almost wholly on the same data, GHCN V3 for land, and ERSST for ocean temperatures.
Even for GISS, though, the upward trends since 2001 are not significant, 0.017c/decade up to 2014.
Many will try to argue that El Nino conditions since April 2014 have put an end to the pause, but it hardly seems very scientific to me to deduce a long term trend from a single weather event.
Either way, the pause up to then was a very real one.